The IEA-International Association for the Evaluation of Educational Achievement is a non-profit-making, non- governmental organisation of research organisations and ministry of education units in over fifty countries. In 1985, the IEA supported a longitudinal, cross-national project exploring the impact of early educational experiences on later school success that was entitled the IEA Preprimary Project. The project was designed in three phases.Phase 1 (1986 - 1992) produced profiles of national policies on the care and education of young children and used a household survey to identify and characterise the major early childhood settings used by families with 4- year-olds. Ireland joined the project late and so did not participate in this phase.Phase 2 (1989 - 1995) used extensive observational and interview data to examine the interactive and structural characteristics of the major early childhood settings and to explore the impact of expectations, curricular and familial factors on children's development at age four.Phase 3 (1993 - 2000) completes the project by describing the child development status at age seven and documenting how the early experiences affect such development. Age seven was selected as the endpoint for the study as it represents the age when all children in the participating countries will have had at least one year of formal schooling.The conceptual framework was broadly based on the ecological systems model of development proposed by Bronfenbrenner. Using the metaphor of a Russian nested doll, Bronfenbrenner portrayed the developing child as being at the centre of an interconnected set of contexts, including those that directly impinge on the child and those that affect the child indirectly, mediated by those with whom the child comes into direct contact.My research sample was drawn from the larger IEA Preprimary Project database and included children in designated disadvantaged (DD) and non-designated disadvantaged (NDD) preschools and schools from across Ireland. The study was designed to identify and analyse the factors in an early educational setting that have an impact on children's development as measured at age 7. Based on the structure of the data, with individual children nested within families and then nested within school settings, a hierarchical linear model (HLM) approach was utilised in the detailed analysis of the data. This method recognises that most educational data exists in a hierarchical ecosystem in which different layers reflect different levels of proximity to a target at the centre of the system. It effectively controlled for the variance that may have been attributable to the individual child when examining the influence of school characteristics on outcome variables. The developmental outcomes were classified along the lines of cognitive and language development, which was in line with the original IEA data. These developmental outcomes have been the focus of considerable international research in the fields of developmental psychology and early education, thus justifying, if not necessitating their examination in an Irish context. I will present the results of my own hierarchical linear analysis of the Irish longitudinal findings, which identify the process (e.g. child activities, teacher behaviour) and structural (class size, availability of materials) variables that are related to subsequent developmental outcomes. These findings will be located in the current Irish early childhood education context (publications, research, governmental programmes) and the broader early childhood education context will be introduced through reference to the international cross- analysis of the longitudinal findings of the project. An example of these findings is the identification of a relationship between level of teacher training and children's language development. In particular, such results are a useful starting point for a discussion of international early childhood education policy (e.g how long should teachers be trained and what training should they receive?) and publications (e.g. OECD reports) and prompt questions about what it is that really matters in the field of early childhood education.